Eur. Phys. J. C (2013) 73: 2629
https://doi.org/10.1140/epjc/s10052-013-2629-x

Regular Article - Theoretical Physics

Direct chargino–neutralino production at the LHC: interpreting the exclusion limits in the complex MSSM

¹ II. Institut für Theoretische Physik, Universität Hamburg, Lupurer Chaussee 149, 22761, Hamburg, Germany
² Instituto de Física de Cantabria, CSIC-UC, 39005, Santander, Spain

^* e-mail: pahlen@ifca.unican.es

Received: 19 July 2013
Revised: 10 October 2013
Published online: 5 November 2013

Abstract

We re-assess the exclusion limits on the parameters describing the supersymmetric (SUSY) electroweak sector of the MSSM obtained from the search for direct chargino–neutralino production at the LHC. We start from the published limits obtained for simplified models, where for the case of heavy sleptons the relevant branching ratio, , is set to one. We show how the decay mode , which cannot be neglected in any realistic model once kinematically allowed, substantially reduces the excluded parameter region. We analyze the dependence of the excluded regions on the phase of the gaugino soft SUSY-breaking mass parameter, M ₁, on the mass of the light scalar tau, , on tanβ as well as on the squark and slepton mass scales. Large reductions in the ranges of parameters excluded can be observed in all scenarios. The branching ratios of charginos and neutralinos are evaluated using a full NLO calculation for the complex MSSM. The size of the effects of the NLO calculation on the exclusion bounds is investigated. We furthermore assess the potential reach of the experimental analyses after collecting 100 fb⁻¹ at the LHC running at 13 TeV.